function binary_search(arr, key) {
  var low = 0,
    high = arr.length - 1;
  while (low <= high) {
    var mid = parseInt((high + low) / 2);
    if (key == arr[mid]) {
      return mid;
    } else if (key > arr[mid]) {
      low = mid + 1;
    } else if (key < arr[mid]) {
      high = mid - 1;
    } else {
      return -1;
    }
  }
}
var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 23, 44, 86];
var result = binary_search(arr, 10);
console.log(result);
